CMP compositions selective for oxide and nitride with high removal rate and low defectivity

ABSTRACT

The invention provides a chemical-mechanical polishing composition containing a ceria abrasive, an ionic polymer of formula I: 
                         
wherein X 1  and X 2 , Z 1  and Z 2 , R 2 , R 3 , and R 4 , and n are as defined herein, and water, wherein the polishing composition has a pH of about 1 to about 4.5. The invention further provides a method of chemically-mechanically polishing a substrate with the inventive chemical-mechanical polishing composition. Typically, the substrate contains silicon oxide, silicon nitride, and/or polysilicon.

BACKGROUND OF THE INVENTION

Compositions and methods for planarizing or polishing the surface of asubstrate are well known in the art. Polishing compositions (also knownas polishing slurries) typically contain an abrasive material in aliquid carrier and are applied to a surface by contacting the surfacewith a polishing pad saturated with the polishing composition. Typicalabrasive materials include silicon dioxide, cerium oxide, aluminumoxide, zirconium oxide, and tin oxide. Polishing compositions aretypically used in conjunction with polishing pads (e.g., a polishingcloth or disk). Instead of, or in addition to, being suspended in thepolishing composition, the abrasive material may be incorporated intothe polishing pad.

As a method for isolating elements of a semiconductor device, a greatdeal of attention is being directed towards a shallow trench isolation(STI) process where a silicon nitride layer is formed on a siliconsubstrate, shallow trenches are formed via etching or photolithography,and a dielectric layer (e.g., an oxide) is deposited to fill thetrenches. Due to variation in the depth of trenches, or lines, formed inthis manner, it is typically necessary to deposit an excess ofdielectric material on top of the substrate to ensure complete fillingof all trenches. The excess dielectric material is then typicallyremoved by a chemical-mechanical planarization process to expose thesilicon nitride layer. When the silicon nitride layer is exposed, thelargest area of the substrate exposed to the chemical-mechanicalpolishing composition comprises silicon nitride, which must then bepolished to achieve a highly planar and uniform surface.

Generally, past practice has been to emphasize selectivity for oxidepolishing in preference to silicon nitride polishing. Thus, the siliconnitride layer has served as a stopping layer during thechemical-mechanical planarization process, as the overall polishing ratedecreased upon exposure of the silicon nitride layer.

Recently, selectivity for oxide polishing in preference to polysiliconpolishing has also been emphasized. For example, the addition of aseries of BRIJ™ and polyethylene oxide surfactants, as well as PLURONIC™L-64, an ethylene oxide-propylene oxide-ethylene oxide triblockcopolymer with an HLB of 15, is purported to increase the polishingselectivity of oxide to polysilicon (see Lee et al., “Effects ofNonionic Surfactants on Oxide-to-Polysilicon Selectivity during ChemicalMechanical Polishing,” J. Electrochem. Soc., 149(8): G477-G481 (2002)).Also, U.S. Pat. No. 6,626,968 discloses that polishing selectivity ofsilicon oxide to polysilicon can be improved through the use of apolymer additive having hydrophilic and hydrophobic functional groupsselected from polyvinylmethylether, polyethylene glycol, polyoxyethylene23 lauryl ether, polypropanoic acid, polyacrylic acid, and polyetherglycol bis(ether).

The STI substrate is typically polished using a conventional polishingmedium and an abrasive-containing polishing composition. However,polishing STI substrates with conventional polishing media andabrasive-containing polishing compositions has been observed to resultin overpolishing of the substrate surface or the formation of recessesin the STI features and other topographical defects such asmicroscratches on the substrate surface. This phenomenon ofoverpolishing and forming recesses in the STI features is referred to asdishing. Dishing is undesirable because dishing of substrate featuresmay detrimentally affect device fabrication by causing failure ofisolation of transistors and transistor components from one another,thereby resulting in short-circuits. Additionally, overpolishing of thesubstrate may also result in oxide loss and exposure of the underlyingoxide to damage from polishing or chemical activity, which detrimentallyaffects device quality and performance.

Thus, there remains a need in the art for polishing compositions andmethods that can provide desirable selectivity of silicon oxide, siliconnitride, and polysilicon and that have suitable removal rates, lowdefectivity, and suitable dishing performance.

BRIEF SUMMARY OF THE INVENTION

The invention provides a chemical-mechanical polishing compositioncomprising, consisting essentially of, or consisting of (a) a ceriaabrasive, (b) an ionic polymer of formula I:

wherein X¹ and X² are independently selected from hydrogen, —OH, and—COOH and wherein at least one of X¹ and X² is —COOH, Z¹ and Z² areindependently O or S, R¹, R², R³, and R⁴ are independently selected fromhydrogen, C₁-C₆ alkyl, and C₇-C₁₀ aryl, and n is an integer of about 3to about 500, and (c) water, wherein the polishing composition has a pHof about 1 to about 4.5.

The invention also provides a method of chemically-mechanicallypolishing a substrate comprising (i) contacting a substrate with apolishing pad and a chemical-mechanical polishing compositioncomprising, consisting essentially of, or consisting of (a) a ceriaabrasive, (b) an ionic polymer of formula I:

wherein X¹ and X² are independently selected from hydrogen, —OH, and—COOH and wherein at least one of X¹ and X² is —COOH, Z¹ and Z² areindependently O or S, R¹, R², R³, and R⁴ are independently selected fromhydrogen, C₁-C₆ alkyl, and C₇-C₁₀ aryl, and n is an integer of about 3to about 500, and (c) water, wherein the polishing composition has a pHof about 1 to about 4.5, (ii) moving the polishing pad and thechemical-mechanical polishing composition relative to the substrate, and(iii) abrading at least a portion of the substrate to polish thesubstrate.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a chemical-mechanical polishing compositioncomprising, consisting essentially of, or consisting of (a) a ceriaabrasive, (b) an ionic polymer of formula I:

wherein X¹ and X² are independently selected from hydrogen, —OH, and—COOH and wherein at least one of X¹ and X² is —COOH, Z¹ and Z² areindependently O or S, R¹, R², R³, and R⁴ are independently selected fromhydrogen, C₁-C₆ alkyl, and C₇-C₁₀ aryl, and n is an integer of about 3to about 500, (c) water, and (d) optionally one or more of the othercomponents described herein, wherein the polishing composition has a pHof about 1 to about 4.5.

The chemical-mechanical polishing composition comprises a ceriaabrasive. As known to one of ordinary skill in the art, ceria is anoxide of the rare earth metal cerium, and is also known as ceric oxide,cerium oxide (e.g., cerium(IV) oxide), or cerium dioxide. Cerium(IV)oxide (CeO₂) can be formed by calcining cerium oxalate or ceriumhydroxide. Cerium also forms cerium(III) oxides such as, for example,Ce₂O₃. The ceria abrasive can be any one or more of these or otheroxides of ceria.

The ceria abrasive can be of any suitable type. As used herein,“wet-process” ceria refers to a ceria prepared by a precipitation,condensation-polymerization, or similar process (as opposed to, forexample, fumed or pyrogenic ceria). A polishing composition of theinvention comprising a wet-process ceria abrasive has been typicallyfound to exhibit lower defects when used to polish substrates accordingto a method of the invention. Without wishing to be bound to aparticular theory, it is believed that wet-process ceria comprisesspherical ceria particles and/or smaller aggregate ceria particles,thereby resulting in lower substrate defectivity when used in theinventive method. An illustrative wet-process ceria is HC60™ ceriacommercially available from Rhodia.

The ceria particles can have any suitable average size (i.e., averageparticle diameter). If the average ceria particle size is too small, thepolishing composition may not exhibit sufficient removal rate. Incontrast, if the average ceria particle size is too large, the polishingcomposition may exhibit undesirable polishing performance such as, forexample, poor substrate defectivity. Accordingly, the ceria particlescan have an average particle size of about 10 nm or more, for example,about 15 nm or more, about 20 nm or more, about 25 nm or more, about 30nm or more, about 35 nm or more, about 40 nm or more, about 45 nm ormore, or about 50 nm or more. Alternatively, or in addition, the ceriacan have an average particle size of about 1,000 nm or less, forexample, about 750 nm or less, about 500 nm or less, about 250 nm orless, about 150 nm or less, about 100 nm or less, about 75 nm or less,or about 50 nm or less. Thus, the ceria can have an average particlesize bounded by any two of the aforementioned endpoints. For example,the ceria can have an average particle size of about 10 nm to about1,000 nm, about 10 nm to about 750 nm, about 15 nm to about 500 nm,about 20 nm to about 250 nm, about 20 nm to about 150 nm, about 25 nm toabout 150 nm, about 25 nm to about 100 nm, or about 50 nm to about 150nm, or about 50 nm to about 100 nm. For non-spherical ceria particles,the size of the particle is the diameter of the smallest sphere thatencompasses the particle. The particle size of the ceria can be measuredusing any suitable technique, for example, using laser diffractiontechniques. Suitable particle size measurement instruments are availablefrom e.g., Malvern Instruments (Malvern, UK).

The ceria particles preferably are colloidally stable in the inventivepolishing composition. The term colloid refers to the suspension ofceria particles in the liquid carrier (e.g., water). Colloidal stabilityrefers to the maintenance of that suspension through time. In thecontext of this invention, an abrasive is considered colloidally stableif, when the abrasive is placed into a 100 mL graduated cylinder andallowed to stand unagitated for a time of 2 hours, the differencebetween the concentration of particles in the bottom 50 mL of thegraduated cylinder ([B] in terms of g/mL) and the concentration ofparticles in the top 50 mL of the graduated cylinder ([T] in terms ofg/mL) divided by the initial concentration of particles in the abrasivecomposition ([C] in terms of g/mL) is less than or equal to 0.5 (i.e.,{[B]−[T]}/[C]≦0.5). More preferably, the value of [B]−[T]/[C] is lessthan or equal to 0.3, and most preferably is less than or equal to 0.1.

The polishing composition can comprise any suitable amount of ceriaabrasive. If the polishing composition of the invention comprises toolittle ceria abrasive, the composition may not exhibit sufficientremoval rate. In contrast, if the polishing composition comprises toomuch ceria abrasive then the polishing composition may exhibitundesirable polishing performance and/or may not be cost effectiveand/or may lack stability. The polishing composition can comprise about10 wt. % or less of ceria, for example, about 9 wt. % or less, about 8wt. % or less, about 7 wt. % or less, about 6 wt. % or less, about 5 wt.% or less, about 4 wt. % or less, about 3 wt. % or less, about 2 wt. %or less, about 1 wt. % or less, about 0.9 wt. % or less, about 0.8 wt. %or less, about 0.7 wt. % or less, about 0.6 wt. % or less of ceria, orabout 0.5 wt. % or less of ceria. Alternatively, or in addition, thepolishing composition can comprise about 0.1 wt. % or more, for example,about 0.2 wt. % or more, about 0.3 wt. % or more, about 0.4 wt. % ormore, about 0.5 wt. % or more, or about 1 wt. % or more of ceria. Thus,the polishing composition can comprise ceria in an amount bounded by anytwo of the aforementioned endpoints. For example, the polishingcomposition can comprise about 0.1 wt. % to about 10 wt. % of ceria,about 0.1 wt. % to about 9 wt. %, about 0.1 wt. % to about 8 wt. %,about 0.1 wt. % to about 7 wt. %, about 0.1 wt. % to about 6 wt. %,about 0.1 wt. % to about 5 wt. % of ceria, about 0.1 wt. % to about 4wt. %, about 0.1 wt. % to about 3 wt. % of ceria, about 0.1 wt. % toabout 2 wt. % of ceria, about 0.1 wt. % to about 1 wt. % of ceria, about0.2 wt. % to about 2 wt. % of ceria, about 0.2 wt. % to about 1 wt. % ofceria, or about 0.3 wt. % to about 0.5 wt. % of ceria. In an embodiment,the polishing composition comprises, at point-of-use, about 0.2 wt. % toabout 0.6 wt. % of ceria (e.g., about 0.4 wt. % of ceria). In anotherembodiment, the polishing composition comprises, as a concentrate, about2.4 wt. % of ceria.

The chemical-mechanical polishing composition comprises an ionic polymerof formula I as described herein.

In certain embodiments, the ionic polymer is of formula I wherein X¹ andX² are both —COOH. In certain embodiments, the ionic polymer is offormula I wherein Z¹ and Z² are both O, and R¹, R², R³, and R⁴ arehydrogen. In certain preferred embodiments, the ionic polymer is offormula I wherein X¹ and X² are both —COOH, Z¹ and Z² are both O, andR¹, R², R³, and R⁴ are hydrogen.

The ionic polymer can have any suitable molecular weight. The ionicpolymer can have an average molecular weight of about 250 g/mol or more,for example, about 300 g/mol or more, about 400 g/mol or more, about 500g/mol or more, about 600 g/mol or more, about 750 g/mol or more, about1,000 g/mol or more, about 1,500 g/mol or more, about 2,000 g/mol ormore, about 2,500 g/mol or more, about 3,000 g/mol or more, about 3,500g/mol or more, about 4,000 g/mol or more, about 4,500 g/mol or more,about 5,000 g/mol or more, about 5,500 g/mol or more, about 6,000 g/molor more, about 6,500 g/mol or more, about 7,000 g/mol or more, or about7,500 g/mol or more. Alternatively, or in addition, the ionic polymercan have an average molecular weight of about 15,000 g/mol or less, forexample, about 14,000 g/mol or less, about 13,000 g/mol or less, about12,000 g/mol or less, about 11,000 g/mol or less, about 10,000 g/mol orless, about 9,000 g/mol or less, about 8,000 g/mol or less, about 7,500g/mol or less, about 7,000 g/mol or less, about 6,500 g/mol or less,about 6,000 g/mol or less, about 5,500 g/mol or less, about 5,000 g/molor less, about 4,500 g/mol or less, about 4,000 g/mol or less, about3,500 g/mol or less, about 3,000 g/mol or less, about 2,500 g/mol orless, or about 2,000 g/mol or less. Thus, the ionic polymer can have anaverage molecular weight bounded by any two of the aforementionedendpoints. For example, the ionic polymer can have an average molecularweight of about 250 g/mol to about 15,000 g/mol, about 250 g/mol toabout 14,000 g/mol, about 250 g/mol to about 13,000 g/mol, about 250g/mol to about 12,000 g/mol, about 250 g/mol to about 11,000 g/mol,about 250 g/mol to about 10,000 g/mol, about 400 g/mol to about 10,000g/mol, about 400 g/mol to about 8,000 g/mol, about 400 g/mol to about6,000 g/mol, about 400 g/mol to about 4,000 g/mol, about 400 g/mol toabout 2,000 g/mol, and the like.

The polishing composition comprises any suitable amount of ionic polymerat the point-of-use. The polishing composition can comprise about 0.001wt. % or more, for example, about 0.005 wt. % or more, about 0.01 wt. %or more, about 0.025 wt. % or more, about 0.05 wt. % or more, about0.075 wt. % or more, or about 0.1 wt. % or more, of the ionic polymer.Alternatively, or in addition, the polishing composition can compriseabout 1 wt. % or less, for example, about 0.9 wt. % or less, about 0.8wt. % or less, about 0.7 wt. % or less, about 0.6 wt. % or less, about0.5 wt. % or less, about 0.4 wt. % or less, or about 0.3 wt. % or less,of the ionic polymer. Thus, the polishing composition can comprise theionic polymer in an amount bounded by any two of the aforementionedendpoints. For example, the polishing composition can comprise about0.001 wt. % to about 1 wt. %, about 0.01 wt. % to about 0.9 wt. %, about0.025 wt. % to about 0.8 wt. %, about 0.05 wt. % to about 0.7 wt. %, orabout 0.1 wt. % to about 0.5 wt. % of the ionic polymer, and the like.

The chemical-mechanical polishing composition optionally comprises oneor more polyvinyl alcohols. The polyvinyl alcohol can be any suitablepolyvinyl alcohol and can be a linear or branched polyvinyl alcohol.Non-limiting examples of suitable branched polyvinyl alcohols are theNichigo G-polymers, such as the OKS-1009 and OKS-1083 products,available from Nippon Gohsei, Japan.

The polyvinyl alcohol can have any suitable degree of hydrolysis. Thedegree of hydrolysis refers to the amount of free hydroxyl groupspresent on the polyvinyl alcohol as compared with the sum of freehydroxyl groups and acetylated hydroxyl groups. Preferably, thepolyvinyl alcohol has a degree of hydrolysis of about 90% or more, e.g.,about 92% or more, about 94% or more, about 96% or more, about 98% ormore, or about 99% or more.

The polyvinyl alcohol can have any suitable molecular weight. Thepolyvinyl alcohol can have an average molecular weight of about 250g/mol or more, for example, about 300 g/mol or more, about 400 g/mol ormore, about 500 g/mol or more, about 600 g/mol or more, about 750 g/molor more, about 1,000 g/mol or more, about 2,000 g/mol or more, about3,000 g/mol or more, about 4,000 g/mol or more, about 5,000 g/mol ormore, about 7,500 g/mol or more, about 10,000 g/mol or more, about15,000 g/mol or more, about 20,000 g/mol or more, about 25,000 g/mol ormore, about 30,000 g/mol or more, about 50,000 g/mol or more, or about75,000 g/mol or more. Alternatively, or in addition, the polyvinylalcohol can have an average molecular weight of about 250,000 g/mol orless, for example, about 200,000 g/mol or less, about 180,000 g/mol orless, about 150,000 g/mol or less, about 100,000 g/mol or less, about90,000 g/mol or less, about 85,000 g/mol or less, about 80,000 g/mol orless, about 75,000 g/mol or less, about 50,000 g/mol or less, about45,000 g/mol or less, about 40,000 g/mol or less, about 35,000 g/mol orless, about 30,000 g/mol or less, about 25,000 g/mol or less, about20,000 g/mol or less, about 15,000 g/mol or less, about 12,500 g/mol orless, or about 10,000 g/mol or less. Thus, the polyvinyl alcohol canhave an average molecular weight bounded by any two of theaforementioned endpoints. For example, the polyvinyl alcohol can have anaverage molecular weight of about 250 g/mol to about 250,000 g/mol, 250g/mol to about 200,000 g/mol, 250 g/mol to about 180,000 g/mol, 250g/mol to about 150,000 g/mol, 250 g/mol to about 100,000 g/mol, about250 g/mol to about 75,000 g/mol, about 250 g/mol to about 50,000 g/mol,about 250 g/mol to about 25,000 g/mol, about 250 g/mol to about 10,000g/mol, about 10,000 g/mol to about 100,000 g/mol, about 10,000 g/mol toabout 75,000 g/mol, about 10,000 g/mol to about 50,000 g/mol, about10,000 g/mol to about 40,000 g/mol, about 50,000 g/mol to about 100,000g/mol, about 75,000 g/mol to about 100,000 g/mol, about 25,000 g/mol toabout 200,000 g/mol, or about 50,000 g/mol to about 180,000 g/mol, andthe like.

The polishing composition comprises any suitable amount of polyvinylalcohol at the point-of-use. The polishing composition can compriseabout 0.001 wt. % or more, for example, about 0.005 wt. % or more, about0.01 wt. % or more, about 0.025 wt. % or more, about 0.05 wt. % or more,about 0.075 wt. % or more, or about 0.1 wt. % or more, of the polyvinylalcohol. Alternatively, or in addition, the polishing composition cancomprise about 1 wt. % or less, for example, about 0.9 wt. % or less,about 0.8 wt. % or less, about 0.7 wt. % or less, about 0.6 wt. % orless, about 0.5 wt. % or less, about 0.4 wt. % or less, or about 0.3 wt.% or less, of the polyvinyl alcohol. Thus, the polishing composition cancomprise the ionic polymer in an amount bounded by any two of theaforementioned endpoints. For example, the polishing composition cancomprise about 0.001 wt. % to about 1 wt. %, about 0.01 wt. % to about0.9 wt. %, about 0.025 wt. % to about 0.8 wt. %, about 0.05 wt. % toabout 0.7 wt. %, or about 0.1 wt. % to about 0.5 wt. % of the polyvinylalcohol, and the like.

The chemical-mechanical polishing composition optionally comprises oneor more nonionic polymers that are different from the polyvinyl alcohol.In accordance with an embodiment of the invention, the polishingcomposition comprises one or more nonionic polymers selected from thegroup consisting of polyalkylene glycols, polyetheramines, polyethyleneoxide/polypropylene oxide copolymers, polyacrylamide,polyvinylpyrrolidone, siloxane polyalkyleneoxide copolymers,hydrophobically modified polyacrylate copolymers, hydrophilic nonionicpolymers, polysaccharides, and mixtures thereof. The nonionic polymersare preferably water-soluble and compatible with other components of thepolishing composition. In some embodiments, the nonionic polymerfunctions as a surfactant and/or wetting agent.

The chemical-mechanical polishing composition can comprise one or morecompounds capable of adjusting (i.e., that adjust) the pH of thepolishing composition (i.e., pH adjusting compounds). The pH of thepolishing composition can be adjusted using any suitable compoundcapable of adjusting the pH of the polishing composition. The pHadjusting compound desirably is water-soluble and compatible with theother components of the polishing composition. Typically, thechemical-mechanical polishing composition has a pH of about 1 to about 7at the point-of-use. Preferably, the chemical-mechanical polishingcomposition has a pH of about 1 to about 4.5 at the point-of-use.

Ionic polymers of formula (I) are acidic in nature. As a consequence,the inventive polishing composition can be formulated to providebuffering capability. Typically, buffering of the polishing compositioncan be accomplished by addition of a basic compound or compounds toadjust the pH value of the polishing composition to a value in the rangeof the pKa value or pKa values of the ionic polymer. Any suitable basiccompound may be used to adjust the pH value to provide for bufferingcapability. Non-limiting examples of suitable basic compounds includesodium hydroxide, potassium hydroxide, ammonium hydroxide, and organicamines such as triethanolamine.

In other embodiments, it is desirable that another compound capable ofadjusting the pH and which is separately capable of buffering an acidicpH of the polishing composition can be added. Accordingly, in either ofthese embodiments, it is desirable that the pH of the polishingcomposition is less than 7.0 (e.g., 6.5+/−0.5, 6.0+/−0.5, 5.5+/−0.5,5.0+/−0.5, 4.5+/−0.5, 4.0+/−0.5, 3.5+/−0.5, 3.0+/−0.5, 2.5+/−0.5,2.0+/−0.5, 1.5+/−0.5, or 1.0+/−0.5). Typically, the pH of the polishingcomposition in either of these embodiments is about 1 to about 4.5 atthe point-of-use. Thus, the compound capable of adjusting the pH of thepolishing composition typically has at least one ionizable group havinga pKa of about 3 to about 7 when measured at 25° C.

The compound capable of adjusting and buffering the pH can be selectedfrom the group consisting of ammonium salts, alkali metal salts,carboxylic acids, alkali metal hydroxides, alkali metal carbonates,alkali metal bicarbonates, borates, and mixtures thereof.

The chemical-mechanical polishing composition optionally furthercomprises one or more additives. Illustrative additives includeconditioners, acids (e.g., sulfonic acids), complexing agents (e.g.,anionic polymeric complexing agents), chelating agents, biocides, scaleinhibitors, dispersants, etc.

A biocide, when present, can be any suitable biocide and can be presentin the polishing composition in any suitable amount. A suitable biocideis an isothiazolinone biocide. The amount of biocide used in thepolishing composition typically is about 1 to about 50 ppm, preferablyabout 10 to about 20 ppm.

It will be understood that any of the components of the polishingcomposition that are acids, bases, or salts (e.g., organic carboxylicacid, base, and/or alkali metal carbonate, etc.), when dissolved in thewater of the polishing composition, can exist in dissociated form ascations and anions. The amounts of such compounds present in thepolishing composition as recited herein will be understood to refer tothe weight of the undissociated compound used in the preparation of thepolishing composition.

The polishing composition can be produced by any suitable technique,many of which are known to those skilled in the art. The polishingcomposition can be prepared in a batch or continuous process. Generally,the polishing composition is prepared by combining the components of thepolishing composition. The term “component” as used herein includesindividual ingredients (e.g., ceria abrasive, ionic polymer, optionalpolyvinyl alcohol, optional nonionic polymer, optional pH adjustor,and/or any optional additive) as well as any combination of ingredients(e.g., ceria abrasive, ionic polymer, optional polyvinyl alcohol,optional nonionic polymer, etc.).

For example, the polishing composition can be prepared by (i) providingall or a portion of the liquid carrier, (ii) dispersing the ceriaabrasive, ionic polymer, optional polyvinyl alcohol, optional nonionicpolymer, optional pH adjustor, and/or any optional additive, using anysuitable means for preparing such a dispersion, (iii) adjusting the pHof the dispersion as appropriate, and (iv) optionally adding suitableamounts of any other optional components and/or additives to themixture.

Alternatively, the polishing composition can be prepared by (i)providing one or more components (e.g., liquid carrier, optionalpolyvinyl alcohol, optional nonionic polymer, optional pH adjustor,and/or any optional additive) in a cerium oxide slurry, (ii) providingone or more components in an additive solution (e.g., liquid carrier,ionic polymer, optional polyvinyl alcohol, optional nonionic polymer,optional pH adjustor, and/or any optional additive), (iii) combining thecerium oxide slurry and the additive solution to form a mixture, (iv)optionally adding suitable amounts of any other optional additives tothe mixture, and (v) adjusting the pH of the mixture as appropriate.

The polishing composition can be supplied as a one-package systemcomprising a ceria abrasive, ionic polymer, optional polyvinyl alcohol,optional nonionic polymer, optional pH adjustor, and/or any optionaladditive, and water. Alternatively, the polishing composition of theinvention is supplied as a two-package system comprising a cerium oxideslurry and an additive solution, wherein the ceria oxide slurry consistsessentially of, or consists of, a ceria abrasive, optional polyvinylalcohol, optional nonionic polymer, optional pH adjustor, and/or anyoptional additive, and water, and wherein the additive solution consistsessentially of, or consists of, ionic polymer, optional polyvinylalcohol, optional nonionic polymer, optional pH adjustor, and/or anyoptional additive. The two-package system allows for the adjustment ofsubstrate global flattening characteristics and polishing speed bychanging the blending ratio of the two packages, i.e., the cerium oxideslurry and the additive solution.

Various methods can be employed to utilize such a two-package polishingsystem. For example, the cerium oxide slurry and additive solution canbe delivered to the polishing table by different pipes that are joinedand connected at the outlet of supply piping. The cerium oxide slurryand additive solution can be mixed shortly or immediately beforepolishing, or can be supplied simultaneously on the polishing table.Furthermore, when mixing the two packages, deionized water can be added,as desired, to adjust the polishing composition and resulting substratepolishing characteristics.

Similarly, a three-, four-, or more package system can be utilized inconnection with the invention, wherein each of multiple containerscontains different components of the inventive chemical-mechanicalpolishing composition, one or more optional components, and/or one ormore of the same components in different concentrations.

In order to mix components contained in two or more storage devices toproduce the polishing composition at or near the point-of-use, thestorage devices typically are provided with one or more flow linesleading from each storage device to the point-of-use of the polishingcomposition (e.g., the platen, the polishing pad, or the substratesurface). As utilized herein, the term “point-of-use” refers to thepoint at which the polishing composition is applied to the substratesurface (e.g., the polishing pad or the substrate surface itself). Bythe term “flow line” is meant a path of flow from an individual storagecontainer to the point-of-use of the component stored therein. The flowlines can each lead directly to the point-of-use, or two or more of theflow lines can be combined at any point into a single flow line thatleads to the point-of-use. Furthermore, any of the flow lines (e.g., theindividual flow lines or a combined flow line) can first lead to one ormore other devices (e.g., pumping device, measuring device, mixingdevice, etc.) prior to reaching the point-of-use of the component(s).

The components of the polishing composition can be delivered to thepoint-of-use independently (e.g., the components are delivered to thesubstrate surface whereupon the components are mixed during thepolishing process), or one or more of the components can be combinedbefore delivery to the point-of-use, e.g., shortly or immediately beforedelivery to the point-of-use. Components are combined “immediatelybefore delivery to the point-of-use” if the components are combinedabout 5 minutes or less prior to being added in mixed form onto theplaten, for example, about 4 minutes or less, about 3 minutes or less,about 2 minutes or less, about 1 minute or less, about 45 s or less,about 30 s or less, about 10 s or less prior to being added in mixedform onto the platen, or simultaneously to the delivery of thecomponents at the point-of-use (e.g., the components are combined at adispenser). Components also are combined “immediately before delivery tothe point-of-use” if the components are combined within 5 m of thepoint-of-use, such as within 1 m of the point-of-use or even within 10cm of the point-of-use (e.g., within 1 cm of the point-of-use).

When two or more of the components of the polishing composition arecombined prior to reaching the point-of-use, the components can becombined in the flow line and delivered to the point-of-use without theuse of a mixing device. Alternatively, one or more of the flow lines canlead into a mixing device to facilitate the combination of two or moreof the components. Any suitable mixing device can be used. For example,the mixing device can be a nozzle or jet (e.g., a high pressure nozzleor jet) through which two or more of the components flow. Alternatively,the mixing device can be a container-type mixing device comprising oneor more inlets by which two or more components of the polishing slurryare introduced to the mixer, and at least one outlet through which themixed components exit the mixer to be delivered to the point-of-use,either directly or via other elements of the apparatus (e.g., via one ormore flow lines). Furthermore, the mixing device can comprise more thanone chamber, each chamber having at least one inlet and at least oneoutlet, wherein two or more components are combined in each chamber. Ifa container-type mixing device is used, the mixing device preferablycomprises a mixing mechanism to further facilitate the combination ofthe components. Mixing mechanisms are generally known in the art andinclude stirrers, blenders, agitators, paddled baffles, gas spargersystems, vibrators, etc.

The polishing composition also can be provided as a concentrate which isintended to be diluted with an appropriate amount of water prior to use.In such an embodiment, the polishing composition concentrate comprisesthe components of the polishing composition in amounts such that, upondilution of the concentrate with an appropriate amount of water, eachcomponent of the polishing composition will be present in the polishingcomposition in an amount within the appropriate range recited above foreach component. For example, the ceria abrasive, ionic polymer, optionalpolyvinyl alcohol, optional nonionic polymer, optional pH adjustor,and/or any optional additive can each be present in the concentrate inan amount that is about 2 times (e.g., about 3 times, about 4 times, orabout 5 times) greater than the concentration recited above for eachcomponent so that, when the concentrate is diluted with an equal volumeof water (e.g., 2 equal volumes water, 3 equal volumes of water, or 4equal volumes of water, respectively), each component will be present inthe polishing composition in an amount within the ranges set forth abovefor each component. Furthermore, as will be understood by those ofordinary skill in the art, the concentrate can contain an appropriatefraction of the water present in the final polishing composition inorder to ensure that the ceria abrasive, ionic polymer, optionalpolyvinyl alcohol, optional nonionic polymer, optional pH adjustor,and/or any optional additive are at least partially or fully dissolvedin the concentrate.

The invention also provides a method of chemically-mechanicallypolishing a substrate comprising (i) contacting a substrate with apolishing pad and the chemical-mechanical polishing composition asdescribed herein, (ii) moving the polishing pad relative to thesubstrate with the chemical-mechanical polishing compositiontherebetween, and (iii) abrading at least a portion of the substrate topolish the substrate.

The chemical-mechanical polishing composition can be used to polish anysuitable substrate and is especially useful for polishing substratescomprising at least one layer (typically a surface layer) comprised of alow dielectric material. Suitable substrates include wafers used in thesemiconductor industry. The wafers typically comprise or consist of, forexample, a metal, metal oxide, metal nitride, metal composite, metalalloy, a low dielectric material, or combinations thereof. The method ofthe invention is particularly useful for polishing substrates comprisingsilicon oxide, silicon nitride, and/or polysilicon, e.g., any one, two,or especially all three of the aforementioned materials.

In certain embodiments, the substrate comprises polysilicon incombination with silicon oxide and/or silicon nitride. The polysiliconcan be any suitable polysilicon, many of which are known in the art. Thepolysilicon can have any suitable phase, and can be amorphous,crystalline, or a combination thereof. The silicon oxide similarly canbe any suitable silicon oxide, many of which are known in the art.Suitable types of silicon oxide include but are not limited toborophosphosilicate glass (BPSG), PETEOS, thermal oxide, undopedsilicate glass, and HDP oxide.

The chemical-mechanical polishing composition of the invention desirablyexhibits a high removal rate when polishing a substrate comprisingsilicon oxide according to a method of the invention. For example, whenpolishing silicon wafers comprising high density plasma (HDP) oxidesand/or plasma-enhanced tetraethyl ortho silicate (PETEOS) and/ortetraethyl orthosilicate (TEOS) in accordance with an embodiment of theinvention, the polishing composition desirably exhibits a silicon oxideremoval rate of about 500 Å/min or higher, 700 Å/min or higher, about1,000 Å/min or higher, about 1,250 Å/min or higher, about 1,500 Å/min orhigher, about 1,750 Å/min or higher, about 2,000 Å/min or higher, about2,500 Å/min or higher, about 3,000 Å/min or higher, about 3,500 Å/min orhigher. In an embodiment, removal rate for silicon oxide can be about4,000 Å/min or higher, about 4,500 Å/min or higher, or about 5,000 Å/minor higher.

The chemical-mechanical polishing composition of the invention desirablyexhibits a low removal rate when polishing a substrate comprisingsilicon nitride according to a method of the invention. For example,when polishing silicon wafers comprising silicon nitride in accordancewith an embodiment of the invention, the polishing composition desirablyexhibits a removal rate of the silicon nitride of about 250 Å/min orlower, for example, about 200 Å/min or lower, about 150 Å/min or lower,about 100 Å/min or lower, about 75 Å/min or lower, about 50 Å/min orlower, or even about 25 Å/min or lower.

The chemical-mechanical polishing composition of the invention desirablyexhibits a low removal rate when polishing a substrate comprisingpolysilicon according to a method of the invention. For example, whenpolishing silicon wafers comprising polysilicon in accordance with anembodiment of the invention, the polishing composition desirablyexhibits a removal rate of polysilicon of about 1,000 Å/min or lower,about 750 Å/min or lower, about 500 Å/min or lower, about 250 Å/min orlower, about 100 Å/min or lower, about 50 Å/min or lower, about 25 Å/minor lower, about 10 Å/min or lower, or even about 5 Å/min or lower.

The polishing composition of the invention desirably exhibits lowparticle defects when polishing a substrate, as determined by suitabletechniques. In a preferred embodiment, the chemical-mechanical polishingcomposition of the invention comprises a wet-process ceria whichcontributes to the low defectivity. Particle defects on a substratepolished with the inventive polishing composition can be determined byany suitable technique. For example, laser light scattering techniques,such as dark field normal beam composite (DCN) and dark field obliquebeam composite (DCO), can be used to determine particle defects onpolished substrates. Suitable instrumentation for evaluating particledefectivity is available from, for example, KLA-Tencor (e.g., SURFSCAN™SP1 instruments operating at a 120 nm threshold or at 160 nm threshold).

A substrate, especially silicon comprising silicon oxide and/or siliconnitride and/or polysilicon, polished with the inventive polishingcomposition desirably has a DCN value of about 20,000 counts or less,e.g., about 17,500 counts or less, about 15,000 counts or less, about12,500 counts or less, about 3,500 counts or less, about 3,000 counts orless, about 2,500 counts or less, about 2,000 counts or less, about1,500 counts or less, or about 1,000 counts or less. Preferablysubstrates polished in accordance with an embodiment of the inventionhas a DCN value of about 750 counts or less, about 500 counts, about 250counts, about 125 counts, or even about 100 counts or less.Alternatively, or in addition, a substrate polishing with thechemical-mechanical polishing composition of the invention desirablyexhibits low scratches as determined by suitable techniques. Forexample, silicon wafers polished in accordance with an embodiment of theinvention desirably have about 250 scratches or less, or about 125scratches or less, as determined by any suitable method known in theart.

The chemical-mechanical polishing composition of the invention can betailored to provide effective polishing at the desired polishing rangesselective to specific thin layer materials, while at the same timeminimizing surface imperfections, defects, corrosion, erosion and theremoval of stop layers. The selectivity can be controlled, to someextent, by altering the relative concentrations of the components of thepolishing composition. When desirable, the chemical-mechanical polishingcomposition of the invention can be used to polish a substrate with asilicon dioxide to polysilicon polishing selectivity of about 5:1 orhigher (e.g., about 10:1 or higher, about 15:1 or higher, about 25:1 orhigher, about 50:1 or higher, about 100:1 or higher, or about 150:1 oreven higher). Also, the chemical-mechanical polishing composition of theinvention can be used to polish a substrate with a silicon nitride topolysilicon polishing selectivity of about 2:1 or higher (e.g., about4:1 or higher, or about 6:1 or higher). Certain formulations can exhibiteven higher silicon dioxide to polysilicon selectivities, such as about20:1 or higher, or even about 30:1 or higher. In a preferred embodiment,the chemical-mechanical polishing composition of the inventionsimultaneously provides selective polishing of silicon dioxide relativeto silicon nitride and selective polishing of silicon dioxide relativeto polysilicon.

The chemical-mechanical polishing composition and method of theinvention are particularly suited for use in conjunction with achemical-mechanical polishing apparatus. Typically, the apparatuscomprises a platen, which, when in use, is in motion and has a velocitythat results from orbital, linear, or circular motion, a polishing padin contact with the platen and moving with the platen when in motion,and a carrier that holds a substrate to be polished by contacting andmoving the substrate relative to the surface of the polishing pad. Thepolishing of the substrate takes place by the substrate being placed incontact with the polishing pad and the polishing composition of theinvention, and then the polishing pad moving relative to the substrate,so as to abrade at least a portion of the substrate to polish thesubstrate.

A substrate can be polished with the chemical-mechanical polishingcomposition using any suitable polishing pad (e.g., polishing surface).Suitable polishing pads include, for example, woven and non-wovenpolishing pads. Moreover, suitable polishing pads can comprise anysuitable polymer of varying density, hardness, thickness,compressibility, ability to rebound upon compression, and compressionmodulus. Suitable polymers include, for example, polyvinylchloride,polyvinylfluoride, nylon, fluorocarbon, polycarbonate, polyester,polyacrylate, polyether, polyethylene, polyamide, polyurethane,polystyrene, polypropylene, coformed products thereof, and mixturesthereof. Soft polyurethane polishing pads are particularly useful inconjunction with the inventive polishing method. Typical pads includebut are not limited to SURFIN™ 000, SURFIN™ SSW1, SPM3100 (commerciallyavailable from, for example, Eminess Technologies), POLITEX™, and FujiboPOLYPAS™ 27. A particularly preferred polishing pad is the EPIC™ D100pad commercially available from Cabot Microelectronics. Anotherpreferred polishing pad is the IC1010 pad available from Dow, Inc.

Desirably, the chemical-mechanical polishing apparatus further comprisesan in situ polishing endpoint detection system, many of which are knownin the art. Techniques for inspecting and monitoring the polishingprocess by analyzing light or other radiation reflected from a surfaceof the substrate being polished are known in the art. Such methods aredescribed, for example, in U.S. Pat. No. 5,196,353, U.S. Pat. No.5,433,651, U.S. Pat. No. 5,609,511, U.S. Pat. No. 5,643,046, U.S. Pat.No. 5,658,183, U.S. Pat. No. 5,730,642, U.S. Pat. No. 5,838,447, U.S.Pat. No. 5,872,633, U.S. Pat. No. 5,893,796, U.S. Pat. No. 5,949,927,and U.S. Pat. No. 5,964,643. Desirably, the inspection or monitoring ofthe progress of the polishing process with respect to a substrate beingpolished enables the determination of the polishing end-point, i.e., thedetermination of when to terminate the polishing process with respect toa particular substrate.

EXAMPLES

These following examples further illustrate the invention but, ofcourse, should not be construed as in any way limiting its scope.

The following abbreviations are used throughout the Examples: removalrate (RR); tetraethyl orthosilicate (TEOS); silicon nitride (SiN);polysilicon (polySi); molecular weight (MW); and polyethylene glycol(PEG).

In the following examples, substrates, TEOS silicon oxide (prepared fromtetraethoxysilane) coated on silicon, HDP (high density plasma) siliconoxide coated on silicon, polysilicon coated on silicon, silicon nitridecoated on silicon, and patterned wafers obtained from Silyb Inc. werepolished using either a MIRRA™ (Applied Materials, Inc.) or a REFLEXION™(Applied Materials, Inc.) tool. The patterned wafers comprised 100 μmsilicon nitride features on silicon oxide-coated substrates. An IC1010™polishing pad (Rohm and Haas Electronic Materials) was used withidentical polishing parameters for all compositions. Standard Mirrapolishing parameters are as follows: IC1010™ pad, downforce=20.68 kPa (3psi), headspeed=85 rpm, platen speed=100 rpm, total flow rate=150mL/min. Removal rates were calculated by measuring the film thickness,using spectroscopic elipsometry, and subtracting the final thicknessfrom the initial thickness.

Example 1

This example demonstrates the effect of a polyethylene glycoldicarboxylic acid on silicon oxide removal rates and silicon oxideversus silicon nitride and polysilicon selectivity.

Separate substrates comprising TEOS-coated silicon, siliconnitride-coated silicon, and polysilicon-coated silicon were polishedwith two different polishing compositions, i.e., Polishing Compositions1A and 1B. Each of the polishing compositions contained 0.4 wt. % ofwet-process ceria in water at a pH of 3.6. Polishing Composition 1A(invention) further contained 0.1 wt. % of a polyethylene glycoldicarboxylic acid having a molecular weight of about 600. PolishingComposition 1B (comparative) further contained a polyacrylic acidpartially esterified with polyethylene glycol.

Following polishing, the removal rates for silicon oxide, siliconnitride, and polysilicon were determined, and the selectivities forsilicon oxide versus silicon nitride and polysilicon were calculated.The removal rate for silicon oxide observed for Polishing Composition 1Ais expressed relative to the removal rate observed for PolishingComposition 1B. The results are set forth in Table 1.

TABLE 1 Polishing SiO Relative SiO/SiN SiO/polysilicon CompositionRemoval Rate Selectivity Selectivity 1A (invention) 1.4 196 58 1B(comparative) 1 53 53

As is apparent from the results set forth in Table 1, the inventivepolishing composition containing a polyethylene glycol dicarboxylic acidexhibited a silicon oxide removal rate that was approximately 1.4 timesgreater, a SiO/SiN selectivity that was approximately 3.7 times greater,and a SiO/polysilicon selectivity that was approximately 15% greater,than the comparative polishing composition containing an ionic polymerwhich is a polyacrylic acid partially esterified with polyethyleneglycol.

Example 2

This example demonstrates the effect of a polyethylene glycoldicarboxylic acid on nitride loss and dishing in the polishing ofpatterned silicon nitride substrates.

Three separate patterned substrates comprising 100 μm silicon nitridefeatures on silicon oxide-coated substrates were polished with threedifferent polishing compositions, i.e., Polishing Compositions 2A-2C.Each of the polishing compositions contained 0.4 wt. % wet-process ceriain water at a pH of 3.6. Polishing Composition 2A (control) did notcontain any polymer. Polishing Compositions 2B and 2C (invention)further contained polyethylene glycol dicarboxylic acids havingmolecular weights of about 3400 and 8000, respectively.

Following polishing, the silicon nitride loss and dishing weredetermined. The silicon nitride loss and dishing are expressed relativeto the silicon nitride loss and dishing observed for PolishingComposition 2B. The results are set forth in Table 2.

TABLE 2 Polishing Silicon Composition nitride loss Dishing 2A (control)30 1.9 2B (invention) 1.0 1 2C (invention) 1.1 1

As is apparent from the results set forth in Table 2, the presence ofpolyethylene glycol dicarboxylic acids in Polishing Compositions 2B and2C resulted in silicon nitride losses that were approximately 30 timesless than the silicon nitride loss exhibited by Polishing Composition2A, which did not contain a polyethylene glycol dicarboxylic acid.Polishing Compositions 2B and 2C exhibited approximately 50% lessdishing than exhibited by Polishing Composition 2A.

Example 3

This example compares silicon oxide removal rates and silicon oxideversus silicon nitride and polysilicon selectivity observed with apolishing composition comprising a polyethylene glycol dicarboxylic acidwith silicon oxide removal rates and silicon oxide versus siliconnitride and polysilicon selectivity observed with polishing compositionscomprising neutral water-soluble polymers containing ether linkages inthe polymer backbones.

Separate substrates comprising TEOS-coated silicon, siliconnitride-coated silicon, and polysilicon-coated silicon were polishedwith four different polishing compositions, i.e., Polishing Compositions3A-3D. Each of the polishing compositions contained 0.4 wt. % ofwet-process ceria in water at a pH of 3.7. Polishing Composition 3A(control) did not further comprise any polymer. Polishing Composition 3B(invention) further comprised 0.1 wt. % of a polyethylene glycoldicarboxylic acid having a molecular weight of about 600. PolishingComposition 3C (comparative) further comprised 0.1 wt. % of a neutralpolysaccharide (HEC QP09L). Polishing Composition 3D (comparative)further comprised 0.1 wt. % of a polyethylene glycol having a molecularweight of about 600.

Following polishing, the removal rates for silicon oxide, siliconnitride, and polysilicon were determined, and the selectivities forsilicon oxide versus silicon nitride and polysilicon were calculated.The removal rates for silicon oxide observed for Polishing Compositions3A, 3C, and 3D are expressed relative to the removal rate observed forPolishing Composition 3B. The results are set forth in Table 3.

TABLE 3 Polishing SiO Relative SiO/SiN SiO/polysilicon CompositionRemoval Rate Selectivity Selectivity 3A (control) 1.4 6.5 32 3B(invention) 1.0 214 44 3C (comparative) 0.24 200 39 3D (comparative) 1.67 99

As is apparent from the results set forth in Table 3, the inventivePolishing Composition 3B exhibited an SiO removal rate that wasapproximately 72% of the SiO removal rate exhibited by the controlpolishing composition, but exhibited an approximately 33-fold higherSiO/SiN selectivity and an approximately 1.4 times greaterSiO/polysilicon selectivity than exhibited by control PolishingComposition 3A. Polishing Composition 3B exhibited a SiO removal ratethat was approximately 63% of the SiO removal rate exhibited byPolishing Composition 3D, which contained a neutral polyethylene glycol,but exhibited an approximately 31-fold higher SiO/SiN selectivity, whileexhibiting a somewhat lower SiO/polysilicon selectivity as compared toPolishing Composition 3D. Polishing Composition 3B also exhibitedapproximately the same SiO/SiN and SiO/polysilicon selectivity, but anapproximately 5-fold greater SiO removal rate, than exhibited byPolishing Composition 3C, which contained a neutral polysaccharide.

Example 4

This example demonstrates the effect on silicon oxide removal rate andsilicon oxide versus silicon nitride and polysilicon selectivityobserved with a polishing composition comprising a polyethylene glycoldicarboxylic acid and further containing linear polyvinyl alcohols.

Separate substrates comprising TEOS-coated silicon and siliconnitride-coated silicon were polished with four different polishingcompositions, i.e., Polishing Compositions 4A-4D. Each of the polishingcompositions contained 0.4 wt. % of wet-process ceria and 0.1 wt. % of apolyethylene glycol dicarboxylic acid having a molecular weight of about600 in water at a pH of 3.7. Polishing Composition 4A did not furthercomprise a polyvinyl alcohol. Polishing Composition 4B further comprised0.1 wt. % of a polyvinyl alcohol having a molecular weight in the rangeof 89,000-98,000. Polishing Composition 4C further comprised 0.1 wt. %of a polyvinyl alcohol having a molecular weight in the range of13,000-18,000. Polishing Composition 4D further comprised 0.1 wt. % of apolyvinyl alcohol having a molecular weight in the range of31,000-50,000.

Following polishing, the removal rates for silicon oxide and siliconnitride were determined, and the selectivities for silicon oxide versussilicon nitride were calculated. The removal rates for silicon oxideobserved for Polishing Compositions 4B-4D are expressed relative to theremoval rate observed for Polishing Composition 4A. The results are setforth in Table 4.

TABLE 4 Polishing SiO Relative SiO/SiN Composition Removal RateSelectivity 4A 1.0 175 4B 0.9 228 4C 1.0 249 4D 1.1 269

As is apparent from the results set forth in Table 4, the use ofpolyvinyl alcohols having various molecular weights did notsubstantially affect the SiO removal rate and maintained high SiO/SiNselectivities for the polishing composition.

Example 5

This example demonstrates the effect on dishing observed with apolishing composition comprising a polyethylene glycol dicarboxylic acidand further containing polyvinyl alcohols.

Four separate patterned substrates comprising 100 μm silicon nitridefeatures on silicon oxide-coated substrates were polished with fourdifferent polishing compositions, i.e., Polishing Compositions 4A-4D asdescribed in Example 4.

Following polishing, the dishing was determined. The dishing observedfor Polishing Compositions 4B-4D are expressed relative to the dishingobserved for Polishing Composition 4A. The results are set forth inTable 5.

TABLE 5 Polishing Composition Dishing 4A 1 4B 0.53 4C 0.68 4D 0.84

As is apparent from the results set forth in Table 5, PolishingCompositions 4B-4D comprising a polyethylene glycol dicarboxylic acidand further comprising polyvinyl alcohols exhibited reduced dishing ascompared to Polishing Composition 4A, which did not further comprise apolyvinyl alcohol, when used to polish patterned substrates comprising100 μm silicon nitride features on silicon oxide-coated substrates, withPolishing Composition 4B, comprising a polyvinyl alcohol having amolecular weight range of 89,000-98,000, exhibiting an approximately 50%reduction in dishing as compared to Polishing Composition 4A.

Example 6

This example demonstrates the effect on silicon oxide removal rate andsilicon oxide versus silicon nitride selectivity observed with apolishing composition comprising a polyethylene glycol dicarboxylic acidand further containing branched polyvinyl alcohols.

Separate substrates comprising TEOS-coated silicon and siliconnitride-coated silicon were polished with five different polishingcompositions, i.e., Polishing Compositions 6A-6E. Each of the polishingcompositions contained 0.4 wt. % of wet-process ceria and 0.1 wt. % of apolyethylene glycol dicarboxylic acid having a molecular weight of about600 in water at a pH of 3.7. Polishing Composition 6A further comprised0.1 wt. % of a linear polyvinyl alcohol having a molecular weight rangeof 31,000-50,000. Polishing Compositions 6B-6E further comprised 0.1 wt.% of branched polyvinyl alcohols OKS-8035, OKS-1009, OKS-8041, andOKS-1083, respectively (Nippon Synthetic Chemical Industry Co., Ltd.,Osaka, Japan).

Following polishing, the removal rates for silicon oxide and siliconnitride were determined, and the selectivities for silicon oxide versussilicon nitride were calculated. The removal rate for silicon oxideobserved for Polishing Compositions 6B-6E are expressed relative to theremoval rate observed for Polishing Composition 6A. The results are setforth in Table 6.

TABLE 6 Polishing Polyvinyl SiO Relative SiO/SiN Composition alcoholRemoval Rate Selectivity 6A Linear 1 244 6B OKS-8035 1.0 164 6C OKS-10090.99 156 6D OKS-8041 0.95 173 6E OKS-1083 0.93 339

As is apparent from the results set forth in Table 6, PolishingCompositions 6B-6E, which contained branched polyvinyl alcohols,exhibited silicon oxide removal rates that were comparable to thesilicon oxide removal rate exhibited by Polishing Composition 6A, whichcontained a linear polyvinyl alcohol. Polishing Compositions 6B-6Eexhibited high SiO/SiN selectivities, with Polishing Composition 6Eexhibiting a SiO/SiN selectivity that was approximately 1.4 timesgreater than the SiO/SiN selectivity exhibited by Polishing Composition6A.

Example 7

This example demonstrates the effect on dishing and nitride lossobserved with a polishing composition comprising a polyethylene glycoldicarboxylic acid and further containing branched polyvinyl alcohols.

Separate patterned substrates comprising 100 μm silicon nitride featureson silicon oxide-coated substrates were polished with five differentpolishing compositions, i.e., Polishing Compositions 6A-6E as describedin Example 6. Following polishing, the silicon nitride loss and dishingwere determined. The silicon nitride loss and dishing observed forPolishing Compositions 6B-6E are expressed relative to the siliconnitride loss and dishing observed for Polishing Composition 6A. Theresults are set forth in Table 7.

TABLE 7 Polishing Polyvinyl Nitride Composition alcohol Dishing loss 6ALinear 1.0 1.0 6B OKS-8035 1.60 1.4 6C OKS-1009 0.94 0.8 6D OKS-8041 1.41.9 6E OKS-1083 1.0 1.0

As is apparent from the results set forth in Table 7, PolishingComposition 6C, which contained the branched polyvinyl alcohol OKS-1009,exhibited approximately 80% of the nitride loss and approximately 94% ofthe dishing exhibited by Polishing Composition 6A.

Example 8

This example demonstrates the effect of the molecular weight ofpolyethylene glycol dicarboxylic acids on silicon oxide removal rate andsilicon oxide versus silicon nitride selectivity in polishingcompositions comprising the same.

Separate substrates comprising TEOS-coated silicon and siliconnitride-coated silicon were polished with three different polishingcompositions, i.e., Polishing Compositions 8A-8C. Each of the polishingcompositions contained 0.4 wt. % of wet-process ceria and 0.1 wt. % of apolyethylene glycol dicarboxylic acid in water at a pH of 3.7. PolishingCompositions 8A-8C comprised polyethylene glycol dicarboxylic acidshaving molecular weights of about 250, about 600, and about 8000,respectively.

Following polishing, the removal rates for silicon oxide and siliconnitride were determined, and the selectivities for silicon oxide versussilicon nitride were calculated. The removal rates for silicon oxideobserved for Polishing Compositions 8A and 8C are expressed relative tothe removal rate observed for Polishing Composition 8B. The results areset forth in Table 8.

TABLE 8 Molecular weight of Polishing polyethylene glycol SiO RelativeSiO/SiN Composition dicarboxylic acid Removal Rate Selectivity 8A 2500.34 40 8B 600 1.0 201 8C 8000 0.99 185

As is apparent from the results set forth in Table 8, PolishingCompositions 8B and 8C, which comprised polyethylene glycol dicarboxylicacids having molecular weights of about 600 and about 8000,respectively, exhibited silicon oxide removal rates that wereapproximately three times greater, and SiO/SiN selectivities that wereapproximately five time greater, than the silicon oxide removal rate andSiO/SiN selectivity exhibited by Polishing Composition 8A, whichcomprised a polyethylene glycol dicarboxylic acid having molecularweight of about 250.

Example 9

This example demonstrates the effect of an organic acid and a nonionicpolymer on the silicon oxide removal rate and silicon oxide versussilicon nitride selectivity exhibited by a polishing compositioncomprising wet-process ceria and a polyethylene glycol dicarboxylicacid.

Separate substrates comprising TEOS-coated silicon and siliconnitride-coated silicon were polished with three different polishingcompositions, i.e., Polishing Compositions 9A-9C. Each of the polishingcompositions contained 0.4 wt. % of wet-process ceria and 0.1 wt. % of apolyethylene glycol dicarboxylic acid in water at a pH of 3.7, andfurther contained different amounts of picolinic acid (i.e., an organicacid) and polyethylene glycol having a molecular weight of about 8000.

Following polishing, the removal rates for silicon oxide and siliconnitride were determined, and the selectivities for silicon oxide versussilicon nitride were calculated. The removal rate for silicon oxideobserved for Polishing Compositions 9B and 9C are expressed relative tothe removal rate observed for Polishing Composition 9A. The results areset forth in Table 9.

TABLE 9 Polishing Picolinic acid Polyethylene SiO Relative SiO/SiNComposition (wt. %) glycol (wt. %) Removal Rate Selectivity 9A 0.03 0.11.0 187 9B 0.008 0.1 0.94 204 9C 0.04 0.005 1.0 218

As is apparent from the results set forth in Table 9, PolishingCompositions 9A-9C exhibited equivalent silicon oxide removal rates andhigh SiO/SiN selectivities of approximately 200.

Example 10

This example demonstrates the effect of an organic acid and a nonionicpolymer on the silicon oxide removal rate and silicon oxide versussilicon nitride selectivity exhibited by a polishing compositioncomprising wet-process ceria and a polyethylene glycol dicarboxylic acidas compared with a polishing composition comprising wet-process ceriaand an ionic polymer which is an acrylicacid-2-acrylamido-2-methylpropane sulfonic acid copolymer.

Separate substrates comprising TEOS-coated silicon and siliconnitride-coated silicon were polished with four different polishingcompositions, i.e., Polishing Compositions 10A-10D. PolishingComposition 10A (invention) contained 0.4 wt. % of wet-process ceria and0.1 wt. % of a polyethylene glycol dicarboxylic acid having a molecularweight of about 600 in water at a pH of 4. Polishing Composition 10B(comparative) contained 0.4 wt. % of wet-process ceria and 0.1 wt. % ofan acrylic acid-2-acrylamido-2-methylpropane sulfonic acid copolymer inwater at a pH of 4. Polishing Composition 10C (invention) contained 0.27wt. % of wet-process ceria, 0.07 wt. % of a polyethylene glycoldicarboxylic acid having a molecular weight of about 600, and 0.07 wt. %of a polyvinyl alcohol having a molecular weight range of 89,000-98,000in water at a pH of 4. Polishing Composition 10D (comparative) contained0.27 wt. % of wet-process ceria and 0.07 wt. % of the acrylicacid-2-acrylamido-2-methylpropane sulfonic acid copolymer in water at apH of 7.

Following polishing, the removal rates for silicon oxide and siliconnitride were determined, and the selectivities for silicon oxide versussilicon nitride were calculated. The removal rate for silicon oxideobserved for Polishing Compositions 10B-10D are expressed relative tothe removal rate observed for Polishing Composition 10A. The results areset forth in Table 10.

TABLE 10 Polishing SiO Relative Rate SiO/SiN Composition RemovalSelectivity 10A (invention) 1.0 203 10B (comparative) 0.16 6 10C(invention) 1.0 171 10D (comparative) 0.49 29

As is apparent from the results set forth in Table 10, PolishingComposition 10A exhibited an approximately 6.4× greater silicon oxideremoval rate and an approximately 34× greater SiO/SiN selectivity thanPolishing Composition 10B. Polishing Composition 10D, which containedapproximately two-thirds of the wet-process ceria as PolishingComposition 10B but had a pH of 7 versus a pH of 4, exhibited anapproximately 2.4× greater silicon oxide removal rate and anapproximately 4.8× greater SiO/SiN selectivity than PolishingComposition 10B. However, Polishing Composition 10C, which contained0.27 wt. % of a wet-process ceria, a polyvinyl alcohol, and apolyethylene glycol dicarboxylic acid, at a pH of 3.5, exhibitedapproximately the same silicon oxide removal rate and an only slightlyless SiO/SiN selectivity than Polishing Composition 10A, which contained0.4 wt. % of wet-process ceria.

Example 11

This example demonstrates the effect on dishing and nitride lossobserved with a polishing composition comprising a polyethylene glycoldicarboxylic acid and further containing a neutral polymer.

Separate patterned substrates comprising 100 μm silicon nitride featureson silicon oxide-coated substrates were polished with three differentpolishing compositions, i.e., Polishing Compositions 11A and 11Bcontaining neutral nonionic polymers and Polishing Composition 11C as aninventive composition, but not containing an added neutral nonionicpolymer. Each of the polishing compositions comprised 0.4 wt. % of awet-process ceria and 0.1 wt. % of a polyethylene glycol dicarboxylicacid having a molecular weight of about 600 in water at a pH of 3.5.Both Polishing Compositions 11A and 11B further comprised a nonionicpolymer. Polishing Composition 11A further comprised a polyvinyl alcoholhaving a molecular weight range of about 89,000-98.000. Composition 11Bfurther comprised a polyethylene glycol having a molecular weight ofabout 8000.

Following polishing, the silicon nitride loss and dishing weredetermined. The silicon nitride loss and dishing observed for PolishingCompositions 11A and 11B are expressed relative to the silicon nitrideloss and dishing observed for Polishing Composition 11C. The results areset forth in Table 11.

TABLE 11 Polishing Silicon Composition nitride loss Dishing 11A 0.75 0.311B 1.05 0.75 11C (control) 1 1

As is apparent from the results set forth in Table 11, PolishingComposition 11A, which comprised a polyvinyl alcohol, exhibited siliconnitride loss and dishing that were approximately 75% and 31% of thesilicon nitride loss and dishing exhibited by Polishing Composition 11C,which did not contain a nonionic polymer. Polishing Composition 11B,which comprised a polyethylene glycol, exhibited approximately the samesilicon nitride loss but approximately 75% of the dishing exhibited byPolishing Composition 11C.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

The invention claimed is:
 1. A chemical-mechanical polishing compositioncomprising: (a) a ceria abrasive, (b) an ionic polymer of formula I:

wherein X¹ and X² are independently selected from hydrogen, —OH, and—COOH and wherein at least one of X¹ and X² is —COOH, Z¹ and Z² areindependently O or S, R¹, R², R³, and R⁴ are independently selected fromhydrogen, C₁-C₆ alkyl, and C₇-C₁₀ aryl, and n is an integer of about 3to about 500, and (c) water, wherein the polishing composition has a pHof about 1 to about 4.5.
 2. The polishing composition of claim 1,wherein X¹ and X² are both —COOH.
 3. The polishing composition of claim2, wherein Z¹ and Z² are both O, and R¹, R², R³, and R⁴ are hydrogen. 4.The polishing composition of claim 1, wherein the ionic polymer has amolecular weight of about 500 daltons to about 10,000 daltons, andwherein n is an integer with a value of 8 or greater.
 5. The polishingcomposition of claim 1, wherein the ionic polymer is present in anamount of about 0.01 wt. % to about 0.5 wt. % of the polishingcomposition.
 6. The polishing composition of claim 1, wherein the ceriaabrasive is a wet-process ceria abrasive.
 7. The polishing compositionof claim 6, wherein the wet-process ceria abrasive is present in anamount of about 0.05 wt. % to about 1 wt. % of the polishingcomposition.
 8. The polishing composition of claim 1, wherein thepolishing composition further comprises a polyvinyl alcohol.
 9. Thepolishing composition of claim 8, wherein the polyvinyl alcohol has amolecular weight of about 20,000 daltons to about 200,000 daltons. 10.The polishing composition of claim 8, wherein the polyvinyl alcohol is abranched polyvinyl alcohol.
 11. A method of chemically-mechanicallypolishing a substrate comprising: (i) contacting a substrate with apolishing pad and a chemical-mechanical polishing compositioncomprising: (a) a ceria abrasive, (b) an ionic polymer of formula I:

wherein X¹ and X² are independently selected from hydrogen, —OH, and—COOH, Z¹ and Z² are independently O or S, R¹, R², R³, and R⁴ areindependently selected from hydrogen, C₁-C₆ alkyl, and C₇-C₁₀ aryl, andn is an integer of about 3 to about 500, and (c) water, wherein thepolishing composition has a pH of about 1 to about 4.5, (ii) moving thepolishing pad and the chemical-mechanical polishing composition relativeto the substrate, and (iii) abrading at least a portion of the substrateto polish the substrate.
 12. The method of claim 11, wherein X¹ and X²are both —COOH.
 13. The method of claim 12, wherein Z¹ and Z² are bothO, and R¹, R², R³, and R⁴ are hydrogen.
 14. The method of claim 11,wherein the ionic polymer has a molecular weight of about 500 daltons toabout 10,000 daltons, and wherein n is an integer with a value of 8 orgreater.
 15. The method of claim 11, wherein the ionic polymer ispresent in an amount of about 0.01 wt. % to about 0.5 wt. % of thepolishing composition.
 16. The method of claim 11, wherein the ceriaabrasive is a wet-process ceria abrasive.
 17. The method of claim 16,wherein the wet-process ceria abrasive is present in an amount of about0.1 wt. % to about 1 wt. % of the polishing composition.
 18. The methodof claim 11, wherein the polishing composition further comprises apolyvinyl alcohol.
 19. The method of claim 18, wherein the polyvinylalcohol has a molecular weight of about 20,000 daltons to about 200,000daltons.
 20. The method of claim 18, wherein the polyvinyl alcohol is abranched polyvinyl alcohol.
 21. The method of claim 11, wherein thesubstrate comprises silicon oxide, and wherein at least a portion of thesilicon oxide is abraded to polish the substrate.
 22. The method ofclaim 21, wherein the substrate further comprises silicon nitride, andwherein at least a portion of the silicon nitride is abraded to polishthe substrate.
 23. The method of claim 21, wherein the substrate furthercomprises polysilicon, and wherein at least a portion of the polysiliconis abraded to polish the substrate.